A vertical antenna comprised of stacked dipoles has a pattern that has omnidirectional gain in azimuth and reduced gain in elevation. The conventional way of stacking dipoles to achieve such a pattern involves the use of a large number of mechanical parts such as metal cylinders or stamped metal assemblies fastened along a feed line connected to a source of signals at one end.
In one antenna of the prior art, four dipoles formed with stamped aluminum are mounted about a metal mast at 90.degree. intervals and parallel thereto. The space between the dipoles and the mast is one-quarter of a wavelength of the operating frequency. The dipoles are interconnected by a coaxial line or a twin-lead cable so as to be energized in phase, and impedance matching networks at each dipole weight the power transmitted or received by that dipole.
In another antenna of the prior art, slotted metal cylinders are coaxially mounted along a hollow metal mast. The slots consist of an air space between a cylinder and the mast which is approximately one-quarter of a wavelength of this design frequency. Each slotted cylinder is connected to a coaxial feed extending within the mast. The center lead of the coaxial feed is connected to a metal cylinder while the outer shield of the coaxial feed is attached to the mast at the point where it is attached to a cylinder.